Over 30 years ago, doctors successfully implanted an artificial heart -- but it was only temporary. It'd keep patients alive until they can get a transplant, but it can’t save a person whose heart has totally failed.

Now in a make-or-break moment, French device maker Carmat is getting ready to test a longer-lasting synthetic heart in people. Businessweek reports.

The 900-gram device has two ventricles (the lower chambers), which are each divided by a membrane of sterile, chemically treated calf tissue. This helps head off blood clots.

Two motorized pumps flex the membrane, sending blood from the ventricles into the arteries.

The device is regulated by embedded sensors and other electronics powered by external, wearable lithium ion batteries.

The artificial heart should last at least five years -- or about 230 million heartbeats -- and can adjust blood flow when the recipient climbs stairs or tucks into bed.

Sound a little like Iron Man? Turns out, the device is the product of a 20-year partnership between cardiac surgeon Alain Carpentier and arms manufacturer Jean-Luc Lagardère of Matra, a company that made missiles and satellites. The megamerger that created European Aeronautic Defence & Space spun off Carmat in 2008.

The synthetic heart has been examined in calves, and models simulated how they work in the human body -- bloodstream flow in hemorrhages, for example. Four test patients suffering from terminal cardiac failure will soon be receiving Carmat’s heart, approved for human trials in France last month.

The trials are a make-or-break moment for Carmat, which is currently training teams to perform the three-hour-long operation to implant their €160,000 ($218,000) heart.

With more than 100,000 cardiac patients awaiting transplants from a supply of about 4,000 human hearts, the company’s stock has almost quintupled in the three years since its initial public offering...

But if Carmat’s trials fail or patients struggle with the heart’s cumbersome rechargeable power supply, the consequences for all involved may be dire.

Meanwhile, IEEE Spectrum reports, a tiny pacemaker that fits inside of a heart chamber has been approved for sale in the E.U. The miniature device was developed by Nanostim, which was recently acquired by biomedical device company St. Jude Medical. More trials are needed before it can be submitted for approval to the U.S. Food and Drug Administration.